Oxygen sorption and desorption properties of Sr–Co–Fe oxide

SrCoFeOxSrCoFeOx has been investigated as a new sorbent for air separation and oxygen removal at high temperatures. X-ray diffraction analysis of a SrCoFeOxSrCoFeOx sample prepared by liquid citrate method reveals that the sample contains an intergrowth (Sr4Fe6-xCoxO13±δ)(Sr4Fe6-xCoxO13±δ), perovskite (SrFe1-xCoxO3-δ)(SrFe1-xCoxO3-δ), and spinel (Co3-xFexO4)(Co3-xFexO4) phase. Both oxygen vacancies (VO¨) and interstitial oxygen ions (Oi″) are involved in the oxygen adsorption and desorption process for SrCoFeOxSrCoFeOx. Compared with the perovskite-type oxide La0.1Sr0.9Co0.9Fe0.1O3-δLa0.1Sr0.9Co0.9Fe0.1O3-δ, SrCoFeOxSrCoFeOx has stronger structure stability in a reducing environment and it also exhibits a larger oxygen sorption capacity at temperatures higher than 800∘C. Meanwhile, unlike La0.1Sr0.9Co0.9Fe0.1O3-δLa0.1Sr0.9Co0.9Fe0.1O3-δ which shows a fast adsorption rate and a slow desorption rate at 900∘C, SrCoFeOxSrCoFeOx shows a fast desorption rate and slow adsorption rate at the same temperature. X-ray diffraction data reveals that SrCoFeOxSrCoFeOx samples sintered at 1140∘C have a higher amount of the intergrowth phase than samples sintered at 950∘C due to slow formation kinetics. X-ray diffraction and thermogravimetric analysis of SrCoFeOxSrCoFeOx samples prepared by the citrate and solid state method show that the synthesis method strongly influences the amount of the three phases in a sample.